1. Field of the Invention:
This invention relates to a range finder using semiconductor position detection elements for use in a camera or the like.
2. Description of the Prior Art:
A large number of methods have been known of range finders using semiconductor position detection elements. An example of the prior art device relatively analogous to the range finder of the present invention is shown in FIG. 1. FIG. 1(a) is a front view of the prior art device and FIG. 1(b) is its side view. An image forming lens 1 is fixedly disposed, and at positions substantially corresponding to the image forming position of this lens 1 are disposed semiconductor position detection elements 2a, 2b divided into two stages to the right and left of the optical axis. A reflecting mirror 3 is fixed at an angle of 45.degree. ahead of the lens 1. The right-hand portion 3a of the reflecting mirror 3 relative to the optical axis is a transparent portion and the left-hand portion 3b, a reflecting mirror portion. A moving mirror 4 is so disposed as to be spaced apart by the length of a basic line BL from the reflecting mirror 3. An optical image of an object O passes through the transparent portion 3a of the reflecting mirror and the lens 1 forms an optical image L.sub.1 on the semiconductor position detection e1ement 2b. On the other hand, the optical image of the object, that is reflected by the moving mirror 4 and by the reflecting mirror portion 3b and passes through the reflecting lens 1, forms an optical image L.sub.2 on the semiconductor position detection element 2a.
FIG. 2 shows the semiconductor position detection elements 2a, 2b of FIG. 1(a) as they are viewed from the top. The optical image L.sub.2 moves when the moving mirror 4 is rotated. The distance of the object can be determined from the rotating position of the moving mirror 4 when the optical image L.sub.2 moves to L.sub.3. Coincidence of the optical image L.sub.1 with L.sub.3 is picked up from signals of the semiconductor position detection elements 2a, 2b and the point of coincidence is electrically determined when both values are most approximate to each other.
The abovementioned method can virtually be established by the fact that the optical image is continuous for the boundary portion 2c between the two semiconductor position detection elements 2a, 2b, but not for the entire surfaces of the detection elements 2a, 2b.
For the reason noted above, a satisfactorily high level of measuring accuracy can not be expected.